Phase change material-based rooftop on public transport for thermal management

Phase change materials(PCMs)are used in buildings and automobiles to control the interior temperature,following to their high thermal storage capacity and energy efficiency.In summer,controlling the interior temperature of vehicles can be difficult,especially in cities where public transportation is excessively crowded.Typically,heating,ventilation,and air-conditioning systems are included to provide thermal comfort inside vehicles,but they use a significant amount fuel,which ultimately have negative impacts on the environment.In this study,a prototype bus model was developed from an actual bus and scaled-down to 1/20th size.A bulb was used as an internal heat source and experiments were conducted under the sun in summer to reflect scenarios of buses stuck in traffic.Various cases were considered by opening and closing the windows and doors and placing the PCM layer on the roof and covering the bulb.The results demonstrate that when the PCM is used to cover the bulb and roof,the interior temperature can drop to the ambient temperature and remain there for a longer period of time.In fact,keeping the windows and doors open results in a significantly lower indoor temperature than when they are closed.The results show that the heat from the engine makes a major contribution to raising the temperature inside of the vehicle.The results from the opened cases can be applied to various forms of public transportation worldwide,but for many closed vehicles,additional ducting systems integrated with PCM may be the best option.

Investigation of phase-change materials for interior temperature regulation in public transport

Regulating the indoor temperature of public transport on hot sunny days is a prime concern,as both the external and internal heat sources play an active role in heat gain.Experimental studies have been carried out on a bus model using sodium sulphate decahydrate as a phase-change material(PCM)that is placed in between the ceiling and the roof.Studies are conducted on a sunny day and also for different cases of external(300-W surface heater)and internal(25-W light bulb)heat sources.The results show that PCM,in the presence of an external heat source,can help to keep the indoor temperature lower and delay the time period for increasing the temperature by absorbing heat during the phase change.On the other hand,the presence of the internal heat source contributes to a detrimental effect on the indoor temperature,which gradually increases with the elapse of time.With the combination of the external and internal heat sources,it is found that the internal heat source plays a dominating factor to raise the indoor temperature.It is revealed from the experimental results that a 12.7-mm single layer and a single PCM are not enough to counter the internal heat of 25 W unless the thickness of the PCM layer is increased to delay the increase in the indoor temperature.An additional PCM layer with a lower melting temperature could be placed at the inner portion of the ceiling to have effective thermal-energy storage by absorbing the substantial heat gain from the internal heat sources.